Cardiovascular

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What it is

The circulatory system includes the heart, blood vessels, and blood. It is further divided into two major circuits: a pulmonary circulation and a systemic circulation. The pulmonary circulation takes deoxygenated blood from the right heart to the lungs for oxygenation, while the systemic circulation delivers oxygenated blood from the left heart to the rest of the body and returns deoxygenated blood to the right heart via large veins. The human circulatory system is closed, meaning that the blood is contained within the vascular network.

Key facts

The circulatory system consists of the heart, blood vessels, and blood. Blood consists of plasma, red blood cells, white blood cells, and platelets. It is circulated around the body, carrying oxygen and nutrients to the tissues and collecting and disposing of waste materials. The digestive system works with the circulatory system to provide the necessary nutrients. The lymphatic system is a subsystem of the circulatory system, consisting of a network of lymphatic vessels, lymph nodes, organs, tissues, and circulating lymph. It is essential for the functioning of the circulatory system, carrying excess plasma away from body tissues and returning it to the heart. The lymphatic system also works with the immune system to provide defense against pathogens.

Source: Circulatory system (CC BY-SA 4.0 (Wikipedia)), retrieved 2026-08-27.